ABSTRACT
Chiral metal-organic frameworks(CMOFs)with enantiomeric subunits have been employed in chiral chemistry.In this study,a CMOF formed from 6-methoxyl-(8S,9R)-cinchonan-9-ol-3-carboxylic acid(HQA)and ZnCl2,{(HQA)(ZnCl2)(2.5H2O)｝n was constructed as a chiral stationary phase(CSP)via an in situ fabrication approach and used for chiral amino acid and drug analyses for the first time.The{(HQA)(ZnCl2)(2.5H2O)}n nanocrystal and the corresponding chiral stationary phase were systematically characterised using a series of analytical techniques including scanning electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy,circular dichroism,X-ray photoelectron spectros-copy,thermogravimetric analysis,and Brunauer-Emmett-Teller surface area measurements.In open-tubular capillary electrochromatography(CEC),the novel chiral column exhibited strong and broad enantioselectivity toward a variety of chiral analytes,including 19 racemic dansyl amino acids and several model chiral drugs(both acidic and basic).The chiral CEC conditions were optimised,and the enantioseparation mechanisms are discussed.This study not only introduces a new high-efficiency member of the MOF-type CSP family but also demonstrates the potential of improving the enantiose-lectivities of traditional chiral recognition reagents by fully using the inherent characteristics of porous organic frameworks.
ABSTRACT
Capillary electrochromatography(CEC)plays a significant role in chiral separation via the double sepa-ration principle,partition coefficient difference between the two phases,and electroosmotic flow-driven separation.Given the distinct properties of the inner wall stationary phase(SP),the separation ability of each SP differs from one another.Particularly,it provides large room for promising applications of open tubular capillary electrochromatography(OT-CEC).We divided the OT-CEC SPs developed over the past four years into six types:ionic liquids,nanoparticle materials,microporous materials,biomaterials,non-nanopolymers,and others,to mainly introduce their characteristics in chiral drug separation.There also added a few classic SPs that occurred within ten years as supplements to enrich the features of each SP.Additionally,we discuss their applications in metabolomics,food,cosmetics,environment,and biology as analytes in addition to chiral drugs.OT-CEC plays an increasingly significant role in chiral separation and may promote the development of capillary electrophoresis(CE)combined with other instruments in recent years,such as CE with mass spectrometry(CE/MS)and CE with ultraviolet light detector(CE/UV).
ABSTRACT
Here,a styrene-based polymer monolithic column poly(VBS-co-TAT-co-AHM)with reversed-phase/hydrophilic interaction liquid chromatography(RPLC/HILIC)bifunctional separation mode was success-fully prepared for capillary electrochromatography by the in situ polymerization of sodium p-styrene sulfonate(VBS)with cross-linkers 3-(acryloyloxy)-2-hydroxypropyl methacrylate(AHM)and 1,3,5-triacryloylhexahydro-1,3,5-triazine(TAT).The preparation conditions of the monolith were optimized.The morphology and formation of the poly(VBS-co-TAT-co-AHM)monolith were confirmed by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR).The separation perfor-mances of the monolith were evaluated systematically.It should be noted that the incorporation of VBS functional monomer can provide π-π interactions,hydrophilic interactions,and ion-exchange in-teractions.Hence,the prepared poly(VBS-co-TAT-co-AHM)monolith can achieve efficient separation of thiourea compounds,benzene series,phenol compounds,aniline compounds and sulfonamides in RPLC or HILIC separation mode.The largest theoretical plate number for N,N'-dimethylthiourea reached 1.7×105 plates/m.In addition,the poly(VBS-co-TAT-co-AHM)monolithic column showed excellent reproducibility and stability.This novel monolithic column has great application value and potential in capillary electrochromatography(CEC).
ABSTRACT
Covalent organic frameworks(COFs)are a novel type of crystalline porous organic polymer materials recently developed.It has several advantages in chromatographic separation field,such as high thermal stability,porosity,structural regularity,and large specific surface area.Here,a novel spherical COF 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde(BPTA)was developed as an electrochromatographic stationary phase for capillary electro-chromatography separation.The COFTTAPB-BPTA modified capillary column was fabricated via a facile in situ growth method at room temperature.The characterization results of scanning electron microscopy(SEM),Fourier transform infrared(FT-IR)spectroscopy,and X-ray diffraction(XRD)confirmed that COF TAPB-BPTA were successfully modified onto the capillary inner surface.The electrochromatography separation performance of the COF TAPB-BPTA modified capillary was investigated.The prepared column demonstrated outstanding separation performance toward alkylbenzenes,phenols,and chlorobenzenes compounds.Furthermore,the baseline separations of non-steroidal anti-inflammatory drugs(NSAIDs)and parabens with good efficiency and high resolution were achieved.Also,the prepared column possessed satisfactory precision of the intra-day runs(n=5),inter-day runs(n=3),and parallel columns(n=3),and the relative standard deviations(RSDs)of the retention times of tested alkylbenzenes were all less than 2.58％.Thus,this new COF-based stationary phase shows tremendous application potential in chromatographic separation field.
ABSTRACT
Homochiral metal-organic frameworks(MOFs)have attracted considerable attention in many fields of research,such as chiral catalysis and chiral chromatography.However,only few homochiral MOFs can be effectively used in capillary electrochromatography(CEC)and their performances are far from adequate.In this study,we successfully synthesized achiral nanocrystalline MIL-53.A facile post-synthetic modi-fication strategy was then implemented to functionalize the product,yielding a homochiral MOF:L-His-NH-MIL-53.This MOF was then employed as a chiral coating in open-tubular CEC mode(OT-CEC),and,as such,it exhibited high enantioselectivities for several racemic drugs.The homochiral MOF and the fabricated capillary coating were systematically characterized using transmission electron microscopy,scanning electron microscopy(with energy-dispersive X-ray spectrometry),Fourier-transform infrared spectroscopy,X-ray diffractometry,thermogravimetric analysis,circular dichroism spectroscopy,Bru-nauer-Emmett-Teller surface area measurements,and X-ray photoelectron spectroscopy.This study is expected to provide a new strategy for the design and establishment of MOF-based chiral OT-CEC systems.
ABSTRACT
Capillary electrochromatography (CEC) is a micro-scale separation technique which is a hybrid between capillary electrophoresis (CE) and liquid chromatography (LC). CEC can be performed in packed, monolithic and open-tubular columns. In recent three years (from 2016 to 2018), enormous attention for CEC has been the development of novel stationary phases. This review mainly covers the development of novel stationary phases for open-tubular and monolithic columns. In particular, some biomaterials attracted increasing interest. There are no significant breakthroughs in technology and principles in CEC. The typical CEC applications, especially chiral separations are described.
ABSTRACT
Objective To simultaneously determine the quantify liquiritin, glycyrrhetinic acid and glycyrrhizic acid inXianlong-Jiedu Yin by high performance capillary electrophoresis (HPCE).Methods HPCE method was performed on a fused silica capillary coates 75μm×85 cm (effective column length 78.5 cm) using 50 mmol/L borax solution-acetonitrile (95:5), with adjusted pH=8.50 as running buffer, lytical 22 kV, and electrokinetic injection 10 s, detected wave length of 254 nm, and temprature maintaining 25℃.Results The liquiritin, glycyrrhetinic acid and glycyrrhizic acid were completely separated within 30 minutes, showing good linear relationship in the range of 12-120, 15-150, 8-160μg/ml (r>0.999 3). The average recoveries were 100.70%, 98.51%, 98.40% withRSD 2.49%, 2.79%, 0.40%, respectively.Conclusions The HPCE was suitable for the determination of liquiritin, glycyrrhetinic acid and glycyrrhizic acid inXianLong-JieDu Yin, which can be used for the quality control.
ABSTRACT
A rapid, reliable and sensitive pressurized capillary electrochromatography-Laser induced fluorescence ( pCEC/LIF ) method with trifluoroacetic acid ( TFA ) pre-column derivation for simultaneous determination of four aflatoxin ( AFB1 , AFB2 , AFG1 , AFG2 ) was developed. This method included separation on a capillary column packed with 1. 8μm C18 particles using 0. 05% FA aqueous solution/methanol (55:45, V/V) as mobile phase at a pump flow rate of 0. 05 mL/min when the split ratio was 1:300. Under the optimum conditions including running voltage of 15 kV, excitation wavelength of 375 nm and emission wavelength of 450 nm, the baseline separation of four aflatoxins was achieved within 10 minutes. The limits of detection (LODs) were 0. 02, 0. 016, 0. 008 and 0. 01 μg/L for AFG1, AFB1, AFG2, AFB2(S/N=3), respectively. The linear detection ranges of AFG1 , AFB1 , AFG2 , AFB2 were 0. 1-10, 0. 1-10, 0. 1-3 and 0. 1-3 μg/L with correlation coefficients (R2) of 0. 9999, 1. 0000, 0. 9995 and 0. 9997, respectively. The established method was applied to analyze the peanut butter, and the recoveries of standard addition experiment were between 90 . 0% and 112 . 0% for all analytes ( RSDs=0 . 5%-1 . 9%) .
ABSTRACT
A pressurized capillary electrochromatography (pCEC) method with post-column detection cell has been developed for the analysis of total alkaloids of cortex Phellodendron amurense Rupr., Rutaceae. The separation of total alkaloids (berberine, palmatine, oatrorrhizine, magnoflorine, phellodendrine, candicine, menisperine) was optimized by compositions of the mobile phase, ionic strength of buffers, pH value, and applied voltage. Separation of total alkaloids was achieved within 11 min by using a mobile phase of Na2HPO4-citric acid solution-acetonitrile (pH 4.00; 3 mM) (60:40, v/v) and applying a voltage of -10 kV. This method showed satisfactory retention times and peak shapes. Meanwhile, a reversed phase high performance liquid chromatography (RP-HPLC) has also been established for the separation of total alkaloids extracted from cortex Phellodendri amurens. Baseline separation of total alkaloids was achieved within 25 min by using a mobile phase of acetonitrile-0.1 percent phosphoric acid with 0.1 g sodium dodecanesulphonate per 100 mL (35:65, v/v). Compared to conventional RP-HPLC, pCEC led to higher column efficiency, less consumption of reagent, and shorter analysis time.
ABSTRACT
A novel silica monolithic stationary phase functionalized with butylaminopropyl ligands for capillary electrochromatography(CEC) has been presented. The monolithic capillary columns were prepared by a sol-gel) process and subsequent a chemical modification. The amino groups on the surface of the stationary phase are meant to generate a substantial anodic electroosmotic flow (EOF). The butyl and propyl groups provide) hydrophobic properties. To evaluate the column performance, effects of buffer pH and organic modifier content on the EOF and electrochromatographic retention behavior of alkylbenzenes, organic acids and anilines were investigated. The monolithic stationary phase exhibited reversed phase (RP) chromatographic behavior toward neutral solutes. The model organic acid anion solutes were separated by the mixed mode mechanism, which comprised RP interaction, weak anion-exchange, and electrophoresis. Basic compounds such as anilines) were well separated on the butylaminopropyl silica monolithic column without peak tailing.
ABSTRACT
Aim: To explore pharmacokinetics of NG-nitro-D-arginine (D-NNA)and NG-nitro-L-arginine (L-NNA)in conscious rats. Methods: The plasma concentration of D-NNA and L-NNA were determined by chiral ligand exchange method with capillary electrochromatography (CEC). Pharmacokinetic parameters were obtained using non-compartment model and were fitted using a computer program DAS. Results: The metabolism of D-NNA and L-NNA exhibited significant isomeric selectivity. The CL and T1/2 of D-NNA and D-NNA were(0.46 ± 0.02) ml·h-1·kg-1 vs (0.17 ± 0.03) ml·h-1·kg-1 (P < 0.05) and (1.44 ± 0.28) h vs (3.48 ± 0.41) h (P < 0.05), respectively. Unidirectional chiral conversion rate of D-NNA to L-NNA was (50.03 ± 8.5)%. Conclusion: The stereoselective pharmacokinetics of N G-nitro-arginine observed maybe due to the unidirectional chiral inversion of D-NNA to L-NNA.